Adamantane is a stable compound having a highly symmetric structure in which four cyclohexane rings are condensed to form a cage. Derivatives of adamantane are known to exhibit a variety of functions, and thus the derivatives are useful sources for drugs high-function industrial materials, etc. For example, Patent Document 1 and 2 etc. disclose studies on use of such derivatives as optical disk substrates, optical fibers, lenses, etc. by virtue of their useful properties such as optical characteristics and heat resistance.
Patent Document 3 discloses studies on use of adamantane esters as a source resin for photoresists on the basis of properties thereof such as acid-sensitivity, dry-etching resistance, and UV transmittance.
In a trend of recent years toward micro-scaling of semiconductor devices, a lithographic step in the production of semiconductor devices is required to be performed with more rigorous micro-scale precision. To satisfy the requirement, there have been studied various micro-pattern formation methods employing a photoresist which functions with respect to a short-wavelength radiation such as a KrF beam an ArF beam, or an F2 excimer laser beam These patterning formation methods employing such exposure techniques have now been developed to liquid-immersion lithography. The new lithographic technique has a drawback in that the range of depth of focus (DOF) where resolution of the photocured resin is ensured becomes considerably narrower with an increase in the numerical aperture (NA) of the lens employed in photolithography. In order to overcome the drawbacks there is a demand for a new photoresist material which can improve DOF characteristics; i.e., a high-refractive-index resist material which ensures resolution within a wide DOF margin (an area ensuring resolution even when the area is apart from the focus), even when a high-NA exposure light is employed.
Meanwhile, a modified alkyl (thio)ether-substituted polymerizable adamantane derivative has never been developed, since synthesis of such a compound is technically difficult.
[Patent Document 1]    Japanese Patent Application Laid-Open (kokai) No. Heisei 6(1994)-305044
[Patent Document 2]    Japanese Patent Application Laid-Open (kokai) No. Heisei 9(1997)-302077
[Patent Document 3]    Japanese Patent Application Laid-Open (kokai) No. Heisei 4(1992)-39665